This invention relates generally to the treatment of waste and more particularly to the treatment of waste generated in residential dwellings.
It has long been known that reeds such as fragmites and bull rushes can be used in filtration beds to remove dissolved pollutants and pathogenic organisms from waste materials. The pollutants are used by the plants as nutrients, and the roots of the reeds filter the water and remove pollutants from it. As exemplified by U.S. Pat. No. 3,770,623 to Seidel, reed beds have been used in the past to treat industrial wastes. However, reed bed treatment facilities have not been wholly free of problems.
One of the most difficult problems involves assuring that the reed plants become established. Successful and efficient operation of the treatment bed requires that the roots penetrate to the bottom of the bed so that they grow thickly and densely. This necessitates that the reeds be planted in high quality top soil and at the same time requires the bottom part of the bed to allow penetration of the roots as well as adequate flow of the effluent. Additionally, the bottom part of the bed should perform a filtering function while the reeds are becoming established. Precautions must also be taken to assure that the top soil does not unduly leach down into the bottom layers of the bed before the plants have become established. Finally, the acid content of the waste should be neutralized in the treatment bed so that acidic solutions are not discharged to the surrounding environment.
The present invention provides an improved method and apparatus for treating wastes and particularly sewage generated in households. In accordance with the invention, each residence is equipped with a septic tank which must only be large enough to handle about one day's quantity of waste. The effluent from each septic tank is directed into a single large reed bed by a piping system that may include standard 2-4 inch plastic plumbing pipes.
The treatment bed is a gravity flow facility having a sloping concrete floor and walls about 2 feet high. A perforated header pipe extends across the high end of the bed to receive the incoming effluent from the septic tanks and distribute it across the width of the bed. The reed bed contains materials arranged in a special matrix which accommodates rapid and thick growth of reeds while at the same time allowing adequate gravity flow of effluent through the bed. A relatively thin layer of small gravel particles covers the floor of the treatment bed and is in turn covered by a thicker layer of larger gravel particles. A transverse strip of crushed limestone occupies part of the gravel layer and acts to neutralize the acidity of the effluent. A layer of hay or straw which overlies the larger gravel layer is covered by a layer of top soil in which the reeds are planted.
This special matrix has a number of advantages. The bottom layer of small gravel particles serves as a sand filter which filters the sewage during the time the reeds are becoming established. The larger gravel allows easy penetration of the roots and permits the effluent to flow through the bed in the desired manner. The crushed limestone serves the same purpose as the large gravel and additionally provides an alkaline presence to neutralize any acids that are present in the effluent. The hay or straw supports the top soil and prevents it from leaching unduly into the gravel where it could clog the gravel and restrict the flow of effluent through the bed. The top soil must remain in place on the hay or straw to provide nourishment for the reeds until their roots have spread out through the lower layers and become firmly established therein.
At the lower end of the reed bed, a perforated collection pipe extends transversely to collect the treated effluent and direct it into a sump located at one corner of the bed. A discharge pipe which delivers the effluent to the sump includes a riser pipe which controls the liquid level in the treatment bed. Downstream from the sump and arranged serially are a chlorinator and a chlorine contact chamber which provide chemical treatment and then discharge the treated water to the ground.